global_settings{assumed_gamma 1}

camera{
  location <1+clock/2, 1.7, -5> // not tied with a 0 in x, y or z
  direction 1.5*z
  look_at <1,.4,2.5>
}

box{
  0,1 rotate 50*y
  scale <1,3,3> // does not affect the line very much
  translate <1,.01,.2> // in my experiments the line appeared as long as the translate x is the same as the camera location x
  rotate 5*x // rotate in y or z makes the line disappear
  hollow
  texture{
    pigment{color rgbf 1} // rgbt shows the line too
  }
  interior{
    media{   // media is needed
      scattering{1, <.1,.9,.2>}  // also works with emission and absorption
    }
  }
}

plane{y, 0 texture{pigment{ rgb .6}} } // line shows on plane and sphere, not on background
sphere{<.8, 0.75, 1.5>, .75 texture{pigment{ rgb 0}}}

light_source{<5, 10, -20> rgb 1.5}

#background{color rgb .2*x}
sky_sphere{pigment{ rgb .1*z}}